Our program is concerned with the role of the renin-angiotensin-aldosterone system in homeostasis, in hypertension and in congestive heart failure. The specific areas of research include: 1) the pathogenesis of experimental renal hypertension in the rabbit and in the dog, 2) the use of angiotensin-II blockade to define the functions of the renin-angiotensin system, 3) the role of the heptapeptide, so-called angiotensin III, in mediating the renin-angiotensin response, 4) the pathophysiology of thoracic caval constriction in the rabbit, and 5) the control of renin release. In the upcomming year, we will continue to place special emphasis on defining the pathogenesis of renal hypertension; studies are being conducted in both the dog ad rabbit. It is planned to give special attention to the changes in the renal circulation following renal artery stenosis in both the dog and the rabbit and to determine how these changes relate to the onset of renal hypertension. The relationship of changes in hypertension to those occurring in congestive heart failure is being studied in a unique model in the rabbit in which both left and right heart failure are produced by the constriction of the aorta above the kidneys. Finally, studies in the area of renin release mechanisms are aimed at defining how the macula densa serves as an intrarenal receptor; this is especially important since it seems increasingly clear that the macula densa is involved in the control of renin release in both experimental and human renovascular hypertension. BIBLIOGRAPHIC REFERENCES: Johnson, J.A., J.O. Davis, R.W. Gotshall, T.E. Lohmeier, J.L. Davis, B. Braverman, and G.E. Tempel. Evidence for an intrarenal beta receptor in the control of renin release. Amer. J. Physiol. 230:410-418, l976. Lohmeier, T.E. and J.O. Davis. The renin-angiotensin-aldosterone system in experimental renal hypertension in the rabbit. Amer. J. Physiol. 230:311-318, l976.